expiry-model

A scuttlebutt model that expires keys

Example

var assert = require("assert")
 
var ExpiryModel = require("expiry-model")
 
var m1 = ExpiryModel()
var m2 = ExpiryModel()
 
var stream = m1.createStream()
stream.pipe(m2.createStream()).pipe(stream)
 
m1.on("update", function (key, value) {
    assert.equal(key, "foo")
    assert.equal(value, "bar")
    console.log("values", key, value)
})
 
m2.set("foo", "bar")

Sync up multiple keys

var assert = require("assert")
 
var ExpiryModel = require("expiry-model")
 
var model1 = ExpiryModel()
var model2 = ExpiryModel()
 
model1.set("1", 1)
model1.set("2", 2)
model1.set("3", 3)
model1.set("foo", { foo: "one" })
model2.set("foo", { bar: "two" })
 
var s1 = model1.createStream()
s1.pipe(model2.createStream()).pipe(s1)
 
process.nextTick(function () {
    var keys = Object.keys(model2.toJSON())
 
    var foo = model1.get("foo")
    var foo2 = model2.get("foo")
 
    assert.deepEqual(foo, foo2)
    assert.deepEqual(foo, {
        foo: "one"
        , bar: "two"
    })
    console.log("foo", foo)
 
    assert.deepEqual(keys, ["1", "2", "3", "foo"])
    console.log("keys", keys)
})
 

Expire keys

var assert = require("assert")
var setTimeout = require("timers").setTimeout
 
var ExpiryModel = require("expiry-model")
 
var model = ExpiryModel({
    maxAge: 5
})
 
model.set("key", "volatile")
 
setTimeout(function () {
    var value = model.get("key")
    assert.equal(value, null)
    console.log("value", value)
}, 10)

Docs

ExpiryModel is like scuttlebutt/model except you can

• configure how long to hold keys in memory before they expire.
• configure when to clean up old data
• configure a cap on how much data to hold in memory
• cleans up the scuttlebutts vector clock over time.
• values set are shallow merged into each other

ExpiryModel(options)

Valid options are maxAge and max and anything else you can pass to lru-cache.

If you set maxAge to be low then the expiry model will only hold keys in memory for that long and it will drop them afterwards, including not passing them onto anyone it replicates to.

maxAge defaults to one day and max defaults to 500.

Installation

npm install expiry-model

Contributors

• Raynos

MIT Licenced